This invention concerns a light weight window construction for transportation vehicles such as buses and the like.
An important goal of the manufacturers and users of transportation vehicles such as buses is to reduce the weight of vehicle components since weight reduction significantly reduces operating costs through reduction of fuel consumption. Lighter weight window construction allows lighter weight supporting structures and can reduce vehicle weight beyond the glazing structure itself.
Furthermore, it is desirable that the window glazing be such that it can be rapidly changed in the event of damage. Glazing materials in transportation vehicles may require frequent changes to eliminate the effects of graffiti and scratching. A significant amount of labor is required with current window constructions for removing the glazing and installing new glazing.
The traditional technique employed for bus windows or the like has a U-shaped channel around the frame and a U-shaped gasket that fits around the entire periphery of the window. The U-shaped gasket is placed around the glazing and the entire gasket and glazing unit is then placed in the frame. The U-shaped gasket forms a moisture seal between the frame and the glazing and isolates the glazing from the metal frame. An advantage of this construction is low initial cost. A disadvantage, however, is the labor intensive effort in replacing damaged glazing since the entire frame must be disassembled to replace the transparent glass or plastic.
More recently, some so-called quick change windows have been developed which allow the glazing to be removed and replaced quickly without the necessity of disassembling the entire frame. This may be accomplished, for example, by utilizing two separate seals to secure the glazing and create a moisture barrier. When the glazing is to be replaced, the interior seal can be quickly removed, allowing the glazing to be replaced without disturbing the balance of the frame or seals. This can yield a significant reduction in the time needed to replace the glazing, but such a construction includes a higher initial cost, a decreased security of retaining the glazing in the frame, particularly if the glazing material is retained in the frame primarily by the gaskets, and generally a heavier assembly.
It is therefore desirable to provide a window construction that is both lightweight and susceptible to quick change of the glazing material.